'There are an awful lot of them in pots by the back door, with that settled look a cat has when it adopts you...'

It is odd how plants creep up on you, without you being aware of what is going on. Somebody once asked me how and why I had fallen so hard for tulips. I could not think of an answer. Now the same thing seems to be happening with geraniums or, more properly, pelargoniums. Paradoxically, it is the ones with good foliage that I find I have been collecting. Not that I ever knew I was collecting them, but there are an awful lot of them now in pots by the back door, with that settled look that a cat has when it adopts you, whether you want it to or not.

The most outstanding is 'Prince of Orange' which has small, neat, rough foliage, an upright, perky habit of growth and a smothering froth of flowers, as showy as anything you ever get with a zonal pelargonium. They do not make big flat heads like a typical zonal. Three or four flowers cluster at the end of a stem in a more relaxed arrangement. Each flower has two quite wide petals at the top and three narrower ones underneath. They are all a rich pink but the upper two petals are marked with dark streaks. The flowers look as though they are fluttering very long eyelashes, which give them a ludicrously coquettish air.

The leaves are scented, supposedly of orange which is how the plant got its name, but the scent is more complex than that. There is also a hint of peppermint, though not as strong as in 'Chocolate Peppermint' which has leaves at least five inches long, smoothly divided into five big lobes. The chocolate bit is in the middle, dark blotches gradually fading at the edges into the dull green of the rest of the leaf.

The flowers are insignificant, as they are with Pelargonium tomentosum which has soft furry leaves on huge sprawling stems. In an uncharacteristically gummy phrase, Gertrude Jekyll described them being "as thick as a fairy's blanket". This is the geranium to use if you want bulk in a pot, but it grows at a staggering pace, so you have to act as referee.

The home of most pelargoniums is South Africa, particularly around the Cape. Their popularity in Britain increased hugely when a new, cheap method of producing sheet glass was invented in the 1820s. Then greenhouses spread at a fantastic rate and plants that needed overwintering under cover, like the South African pelargoniums, became much more common.

The gardener Francis Masson first sent back some of the species from which our garden varieties were bred. He set off with Captain Cook to the Cape in 1772 and spent three years there plant hunting for Kew. Thanks to his pioneering work, pelargoniums were enthusiastically taken up by Victorian gardeners in formal, geometric beds. The gardeners at Drumlanrig Castle in Scotland used at least 30,000 pelargoniums in their displays each year. The ones with scented leaves were used as indoor pot plants, ranged along window ledges or displayed on stands where their foliage, brushed in passing, would scent a room.

Writing in the Journal of Horticulture in 1863, a "Wiltshire Rector" confessed that he had been infected by a "geranium fever of a very scarlet type" for the past 10 years. Each summer, he filled 18 fancy beds in his lawn with geraniums and complained that, in consequence, for seven months of the year his house was impossible to live in. "Laundry full, study windows full, dressing-room ditto, and if I go down into my cellar I knock my head against Tom Thumbs hanging from the ceiling."

That is the crux of the problem. Although geraniums give a fabulous display for perhaps five months of the year, you still have to accommodate them in some form for the other seven.

The usual way to propagate is to take cuttings in late summer, using soft tip cuttings which are two or three inches long. Make the cut just below a leaf joint. Take off all the lower leaves, leaving just the tuft of growth at the tip of the cutting.

Set the cuttings in compost around the edge of a five-inch pot. You do not need rooting powder. Water the pot and keep it shaded from direct sun. Do not cover. The cuttings root quickly. When they sprout fresh growth, they have struck. Pot into individual pots and keep them in a frost-free place over winter. Pinch out the top of the new plant when it is about six inches tall. This will make it sturdy and stocky.

This method gives you good-sized plants to set outside in May. You can overwinter the mother plant and take cuttings from it in early spring but, of course, these will not have made so much growth by the time you set them out in May. Scented-leaved pelargoniums can be brought in in their pots and used as house plants through the winter.

Victorian gardeners produced batches that flowered all through the year. Spring cuttings make the best winter-flowering plants. When the cuttings have rooted, pot them on and disbud them all summer, pinching back the growing tip and the side shoots to make a strong framework. Six weeks before you want the plants to flower, stop disbudding.

William Taylor, Victorian head gardener at Longleat, managed to get his winter stocks of 'Vesuvius', a zonal variety still available, to produce at least 20 winter trusses of flower at once by this method.

I dare not even think about 'Vesuvius'. The scented-leaved mob are more than enough to occupy one lifetime. The most recent arrival is 'Purple Unique'. The Unique pelargoniums, many of which have the wild South African species P. fulgidum as a parent, make tall, quite shrubby plants with scented leaves and flowers that look much more like regal pelargoniums than zonal ones. The foliage of 'Purple Unique' is a soft, matt green and smells deliciously of absinthe mixed with cough mixture.

'Attar of Roses' is much less rumbustious. The leaves are small, deeply cut and smell, as you might expect, of roses. The heads of flower are much less showy than 'Prince of Orange' or 'Purple Unique': small, in perfect balance with the foliage and very pale pink.

The next thing we can hope for is that breeders will find a way to cross two frost-hardy species of pelargonium, P endlicherianum and P quercetorum, natives of Turkey and Iraq, with the huge family of South African species. Then we will have the perfect pelargonium - one that can stay out all winter.

Membership of The British Pelargonium and Geranium Society costs pounds 6.50 a year (134 Montrose Avenue, Welling, Kent DA16 2QY). Look out in secondhand bookshops for D Clifford's Pelargoniums (Blandford Press, 1958). Specialist nurseries include Brian Sulman Pelargoniums, 54 Kingsway, Mildenhall, Suffolk IP28 7HR (01638 712297 mail order); Denmead Geranium Nurseries, Hambledon Road, Denmead, Waterlooville, Hampshire PO7 6PS (01705 240081); Fibrex Nurseries, Honeybourne Road, Pebworth, Stratford-on-Avon, Warwickshire CV37 8XT (01789 720788); Vernon Geranium Nursery, Cuddington Way, Cheam, Sutton, Surrey SM2 7JB (0181-393 7616).